Strength
Manual Muscle Testing (MRC Scale)
Strength of individual muscles or muscle groups, graded ordinally from 0 (no contraction) to 5 (normal power). Fast, equipment-free, and universally used, though subjective and least precise at the higher grades.
Administration
- Position and stabilize the proximal segment so the target muscle works in isolation.
- Grades 0 to 2 are tested in a gravity-eliminated (gravity-minimized) plane; grades 3 and above are tested against gravity.
- Grade 3 is the pivot point: full range against gravity with no added resistance.
- For grades 4 and 5, apply manual resistance perpendicular to the moving segment at the end of available range.
- Test bilaterally for comparison and record the position and plane used.
Normative data
| Grade | Name | Criteria |
|---|---|---|
| 5 | Normal | Full ROM against gravity, holds against maximal resistance |
| 4 | Good | Full ROM against gravity, holds against moderate resistance |
| 3 | Fair | Full ROM against gravity, tolerates no added resistance |
| 2 | Poor | Full ROM only with gravity eliminated |
| 1 | Trace | Visible or palpable contraction, no joint movement |
| 0 | Zero | No visible or palpable contraction |
Grade 3 (movement against gravity) is the critical dividing point of the scale. Grade 4 spans a wide range of strength and is the least precise grade; consider handheld dynamometry when finer resolution is needed.
Source: MRC / StatPearls
| Grade | Meaning |
|---|---|
| 5 | Holds against maximal resistance |
| 4+ | Holds against nearly maximal resistance |
| 4 | Holds against moderate resistance |
| 4- | Holds against slight to moderate resistance |
| 3+ | Full ROM against gravity, tolerates minimal resistance |
| 3 | Full ROM against gravity, no resistance |
| 3- | More than half ROM against gravity, not full |
| 2+ | Initiates movement against gravity but far less than full ROM |
| 2 | Full ROM gravity-eliminated |
| 2- | Partial ROM gravity-eliminated |
Plus/minus grades are widely used clinical convention rather than part of the original MRC scale, and they increase subjectivity. Use one grading framework consistently within a patient record.
Source: Clinical convention (Hislop & Montgomery)
Interpretation
Report the grade, the plane tested, and the muscle. MMT is quick and reliable at the lower grades but subjective and imprecise at grades 4 to 5, where a large true-strength range collapses into one or two grades. For tracking change at higher strength, an objective handheld dynamometer is more sensitive.
References
- Medical Research Council muscle scale, 0 to 5. Original 1943 MRC publication; grade definitions reproduced in StatPearls, Muscle Strength Grading. PubMed